Purpose: The purpose of this study is to identify gaps in support for parents of children with Hypoplastic Left Heart Syndrome. Design and methods: Using a mixed-methods approach, the researchers first studied the parental and care team experience through interviews of Hypoplastic Left Heart Syndrome mothers and members of the inter-professional care team and then conducted an international survey of 690 Hypoplastic Left Heart Syndrome primary caregivers to validate the qualitative findings. Results: Parental and care team interviews revealed three main gaps in parental support, including lack of open communication, unrealistic parental expectations, and unclear inter-professional team roles. Survey results found that parents whose children were diagnosed with Hypoplastic Left Heart Syndrome after birth indicated significant dissatisfaction with the care team’s open communication and welcoming of feedback (p = 0.008). As parents progress through the stages of surgical intervention, they also indicate significant dissatisfaction with the care team’s anticipation of parental emotional needs and provision of coping resources (p = 0.003). Conclusions: Parental support interventions should focus on providing resources to help parents cope, helping the care team model open communication, and welcoming feedback on the parental experience. Practice implications: Interventions should be piloted with parents who are in the later stages of the surgical intervention timeline or whose children were diagnosed after birth as they are the populations who perceived the least support within this study.